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Investments in Unconsolidated Affiliates - Activity Related to Partnership's Investments in Unconsolidated Affiliates (Parenthetical) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Feb. 06, 2018
Schedule Of Equity Method Investments [Line Items]
Return of capital from unconsolidated affiliate	$ 13.2	$ 3.5	$ 5.5
Contribution of property, plant and equipment to investment in unconsolidated affiliates			16.0
Targa Resources Partners LP [Member] | Little Missouri 4 [Member]
Schedule Of Equity Method Investments [Line Items]
Return of capital from unconsolidated affiliate			$ 8.0
Targa Resources Partners LP [Member] | T2 LaSalle and T2 Eagle Ford [Member]
Schedule Of Equity Method Investments [Line Items]
Unamortized excess fair value	$ 21.6
Preliminary estimated useful lives of the underlying assets	20 years
GCX DevCo JV [Member]
Schedule Of Equity Method Investments [Line Items]
Ownership interest	20.00%	20.00%	20.00%
GCX DevCo JV [Member] | GCX [Member]
Schedule Of Equity Method Investments [Line Items]
Ownership interest	25.00%	25.00%	25.00%	25.00%

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Contribution of Property plant and equipment to investment in unconsolidated affiliates.

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+ References

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-Publisher FASB
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